1. Field
One or more embodiments of the following description relate to an apparatus and method for reducing three-dimensional (3D) visual fatigue that a user feels when viewing a 3D image. More particularly, one or more embodiments of the following description relate to an apparatus and method for reducing 3D visual fatigue that may estimate a user-to-screen distance from a screen to a user, may calculate a user-to-3D object distance based on the estimated user-to-screen distance and a parallax of a 3D image, may predict 3D visual fatigue of the user based on the estimated user-to-screen distance and the calculated user-to-3D object distance, and may control the 3D image based on the predicted 3D visual fatigue.
2. Description of the Related Art
A three-dimensional (3D) image or a stereoscopic image refers to an image that enables a user to experience a realistic stereoscopic effect based on different parallax images viewed by left and right eyes of the user.
A method of displaying a 3D image is referred to as a 3D display method, and is broadly classified into a viewpoint representation method and an aerial image display method.
The viewpoint representation method may enable each viewpoint image to be displayed on a display device, to represent images corresponding to left and right eyes of a user. The viewpoint representation method may include, for example, a stereoscopic display method and a multi-view display method.
In the viewpoint representation method, each viewpoint image may appear on a display screen in the same manner as a two-dimensional (2D) display method.
The aerial image display method may enable voxels, namely pixels suspended in space, to be formed to generate a 3D image, regardless of a concept of a viewpoint. A representative example of the aerial image display method includes a holographic display method.
The 3D display method has an advantage in that a highly realistic 3D representation enables a highly immersive video experience. However, since different image information is represented based on left and right viewpoints, visual fatigue is highly likely to occur compared with a 2D image.
Visual fatigue caused by the 3D display method is known as 3D visual fatigue.
3D visual fatigue may occur due to various causes. Severe fatigue may cause headaches, dizziness, or vomiting.
The 3D visual fatigue may be caused by unnatural depth information of images viewed by left and right eyes, or by a conflict between the two eyes.
A representative example of the conflict includes a convergence-accommodation conflict that may frequently occur in most 3D display methods.
A fatigue level may be increased when a 3D image is displayed relatively far away from a screen.
Despite a long history of research, a problem of 3D visual fatigue caused by the 3D display method still remains.
Even a recent 3D display method is unable to overcome the problem of 3D visual fatigue since various and complex factors cause 3D visual fatigue, and there is no standardized means for measuring and evaluating the fatigue level. Additionally, any systematic method of removing and reducing visual fatigue is not established.
In particular, it is impossible to fundamentally solve a fatigue phenomenon caused by the above-described convergence-accommodation conflict, when considering characteristics of the viewpoint representation method. The fatigue phenomenon has been regarded as a main problem occurring when viewing a 3D image with a high stereoscopic effect.
Accordingly, there is a demand to solve the 3D visual fatigue phenomenon, considered as a main weak point of 3D display, in order to achieve commercialization and market expansion of the 3D display.